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Yu Z, He W, Hu S, Ren Z, Wan S, Cheng X, Hu Y, Jiang T. Creating Anti-Chiral Exceptional Points in Non-Hermitian Metasurfaces for Efficient Terahertz Switching. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2024:e2402615. [PMID: 38757557 DOI: 10.1002/advs.202402615] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2024] [Revised: 04/28/2024] [Indexed: 05/18/2024]
Abstract
Non-Hermitian degeneracies, also known as exceptional points (EPs), have presented remarkable singular characteristics such as the degeneracy of eigenvalues and eigenstates and enable limitless opportunities for achieving fascinating phenomena in EP photonic systems. Here, the general theoretical framework and experimental verification of a non-Hermitian metasurface that holds a pair of anti-chiral EPs are proposed as a novel approach for efficient terahertz (THz) switching. First, based on the Pancharatnam-Berry (PB) phase and unitary transformation, it is discovered that the coupling variation of ±1 spin eigenstates will lead to asymmetric modulation in two orthogonal linear polarizations (LP). Through loss-induced merging of a pair of anti-chiral EPs, the decoupling of ±1 spin eigenstates are then successfully realized in a non-Hermitian metasurface. Final, the efficient THz modulation is experimentally demonstrated, which exhibits modulation depth exceeding 70% and Off-On-Off switching cycle less than 9 ps in one LP while remains unaffected in another one. Compared with conventional THz modulation devices, the metadevice shows several figures of merits, such as a single frequency operation, high modulation depth, and ultrafast switching speed. The proposed theory and loss-induced non-Hermitian device are general and can be extended to numerous photonic systems varying from microwave, THz, infrared, to visible light.
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Affiliation(s)
- Zhongyi Yu
- College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha, 410073, P. R. China
| | - Weibao He
- College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha, 410073, P. R. China
| | - Siyang Hu
- College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha, 410073, P. R. China
| | - Ziheng Ren
- College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha, 410073, P. R. China
| | - Shun Wan
- College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha, 410073, P. R. China
| | - Xiang'ai Cheng
- College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha, 410073, P. R. China
| | - Yuze Hu
- Institute for Quantum Science and Technology, College of Science, National University of Defense Technology, Changsha, 410073, P. R. China
| | - Tian Jiang
- Institute for Quantum Science and Technology, College of Science, National University of Defense Technology, Changsha, 410073, P. R. China
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Yang H, Ji G, Choi M, Park S, An H, Lee HT, Jeong J, Park YD, Kim K, Park N, Jeong J, Kim DS, Park HR. Suppressed terahertz dynamics of water confined in nanometer gaps. SCIENCE ADVANCES 2024; 10:eadm7315. [PMID: 38657066 PMCID: PMC11042745 DOI: 10.1126/sciadv.adm7315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2023] [Accepted: 03/21/2024] [Indexed: 04/26/2024]
Abstract
Nanoconfined waters exhibit low static permittivity mainly due to interfacial effects that span about one nanometer. The characteristic length scale may be much longer in the terahertz (THz) regime where long-range collective dynamics occur; however, the THz dynamics have been largely unexplored because of the lack of a robust platform. Here, we use metallic loop nanogaps to sharply enhance light-matter interactions and precisely measure real and imaginary THz refractive indices of nanoconfined water at gap widths ranging from 2 to 20 nanometers, spanning mostly interfacial waters all the way to quasi-bulk waters. We find that, in addition to the well-known interfacial effect, the confinement effect also contributes substantially to the decrease in the complex refractive indices of the nanoconfined water by cutting off low-energy vibrational modes, even at gap widths as large as 10 nanometers. Our findings provide valuable insights into the collective dynamics of water molecules which is crucial to understanding water-mediated processes.
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Affiliation(s)
- Hyosim Yang
- Department of Physics, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
| | - Gangseon Ji
- Department of Physics, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
| | - Min Choi
- Department of Chemistry, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
| | - Seondo Park
- Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea
| | - Hyeonjun An
- Department of Physics, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
| | - Hyoung-Taek Lee
- Department of Physics, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
| | - Joonwoo Jeong
- Department of Physics, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
| | - Yun Daniel Park
- Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea
| | - Kyungwan Kim
- Department of Physics, Chungbuk National University, Cheongju 28644, Republic of Korea
| | - Noejung Park
- Department of Physics, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
| | - Jeeyoon Jeong
- Department of Physics and Institute for Quantum Convergence Technology, Kangwon National University, Chuncheon 24341, Republic of Korea
| | - Dai-Sik Kim
- Department of Physics, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea
| | - Hyeong-Ryeol Park
- Department of Physics, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
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Duan S, Su X, Qiu H, Jiang Y, Wu J, Fan K, Zhang C, Jia X, Zhu G, Kang L, Wu X, Wang H, Xia K, Jin B, Chen J, Wu P. Linear and phase controllable terahertz frequency conversion via ultrafast breaking the bond of a meta-molecule. Nat Commun 2024; 15:1119. [PMID: 38321010 PMCID: PMC10847458 DOI: 10.1038/s41467-024-45416-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2023] [Accepted: 01/22/2024] [Indexed: 02/08/2024] Open
Abstract
The metasurface platform with time-varying characteristics has emerged as a promising avenue for exploring exotic physics associated with Floquet materials and for designing photonic devices like linear frequency converters. However, the limited availability of materials with ultrafast responses hinders their applications in the terahertz range. Here we present a time-varying metasurface comprising an array of superconductor-metal hybrid meta-molecules. Each meta-molecule consists of two meta-atoms that are "bonded" together by double superconducting microbridges. Through experimental investigations, we demonstrate high-efficiency linear terahertz frequency conversion by rapidly breaking the bond using a coherent ultrashort terahertz pump pulse. The frequency and relative phase of the converted wave exhibit strong dependence on the pump-probe delay, indicating phase controllable wave conversion. The dynamics of the meta-molecules during the frequency conversion process are comprehensively understood using a time-varying coupled mode model. This research not only opens up new possibilities for developing innovative terahertz sources but also provides opportunities for exploring topological dynamics and Floquet physics within metasurfaces.
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Affiliation(s)
- Siyu Duan
- Research Institute of Superconductor Electronics (RISE) & Key Laboratory of Optoelectronic Devices and Systems with Extreme Performances of MOE, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210023, China
- Purple Mountain Laboratories, Nanjing, 211111, China
| | - Xin Su
- Research Institute of Superconductor Electronics (RISE) & Key Laboratory of Optoelectronic Devices and Systems with Extreme Performances of MOE, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210023, China
- College of Engineering and Applied Sciences, Nanjing University, Nanjing, 210023, China
| | - Hongsong Qiu
- Research Institute of Superconductor Electronics (RISE) & Key Laboratory of Optoelectronic Devices and Systems with Extreme Performances of MOE, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210023, China
| | - Yushun Jiang
- Research Institute of Superconductor Electronics (RISE) & Key Laboratory of Optoelectronic Devices and Systems with Extreme Performances of MOE, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210023, China
| | - Jingbo Wu
- Research Institute of Superconductor Electronics (RISE) & Key Laboratory of Optoelectronic Devices and Systems with Extreme Performances of MOE, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210023, China.
- Purple Mountain Laboratories, Nanjing, 211111, China.
| | - Kebin Fan
- Research Institute of Superconductor Electronics (RISE) & Key Laboratory of Optoelectronic Devices and Systems with Extreme Performances of MOE, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210023, China
- Purple Mountain Laboratories, Nanjing, 211111, China
| | - Caihong Zhang
- Research Institute of Superconductor Electronics (RISE) & Key Laboratory of Optoelectronic Devices and Systems with Extreme Performances of MOE, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210023, China
- Purple Mountain Laboratories, Nanjing, 211111, China
| | - Xiaoqing Jia
- Research Institute of Superconductor Electronics (RISE) & Key Laboratory of Optoelectronic Devices and Systems with Extreme Performances of MOE, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210023, China
- Purple Mountain Laboratories, Nanjing, 211111, China
| | - Guanghao Zhu
- Research Institute of Superconductor Electronics (RISE) & Key Laboratory of Optoelectronic Devices and Systems with Extreme Performances of MOE, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210023, China
| | - Lin Kang
- Research Institute of Superconductor Electronics (RISE) & Key Laboratory of Optoelectronic Devices and Systems with Extreme Performances of MOE, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210023, China
- Purple Mountain Laboratories, Nanjing, 211111, China
| | - Xinglong Wu
- National Laboratory of Solid State Microstructures, Nanjing University, Nanjing, 210093, China
- School of Physics, Nanjing University, Nanjing, 210093, China
| | - Huabing Wang
- Research Institute of Superconductor Electronics (RISE) & Key Laboratory of Optoelectronic Devices and Systems with Extreme Performances of MOE, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210023, China
- Purple Mountain Laboratories, Nanjing, 211111, China
| | - Keyu Xia
- College of Engineering and Applied Sciences, Nanjing University, Nanjing, 210023, China.
- National Laboratory of Solid State Microstructures, Nanjing University, Nanjing, 210093, China.
- Shishan Laboratory, Suzhou Campus of Nanjing University, Suzhou, 215000, China.
| | - Biaobing Jin
- Research Institute of Superconductor Electronics (RISE) & Key Laboratory of Optoelectronic Devices and Systems with Extreme Performances of MOE, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210023, China.
- Purple Mountain Laboratories, Nanjing, 211111, China.
| | - Jian Chen
- Research Institute of Superconductor Electronics (RISE) & Key Laboratory of Optoelectronic Devices and Systems with Extreme Performances of MOE, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210023, China
- Purple Mountain Laboratories, Nanjing, 211111, China
| | - Peiheng Wu
- Research Institute of Superconductor Electronics (RISE) & Key Laboratory of Optoelectronic Devices and Systems with Extreme Performances of MOE, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210023, China
- Purple Mountain Laboratories, Nanjing, 211111, China
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Ding F, Deng Y, Meng C, Thrane PCV, Bozhevolnyi SI. Electrically tunable topological phase transition in non-Hermitian optical MEMS metasurfaces. SCIENCE ADVANCES 2024; 10:eadl4661. [PMID: 38306421 PMCID: PMC10836917 DOI: 10.1126/sciadv.adl4661] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2023] [Accepted: 01/02/2024] [Indexed: 02/04/2024]
Abstract
Exceptional points (EPs), unique junctures in non-Hermitian open systems where eigenvalues and eigenstates simultaneously coalesce, have gained notable attention in photonics because of their enthralling physical principles and unique properties. Nonetheless, the experimental observation of EPs, particularly within the optical domain, has proven rather challenging because of the grueling demand for precise and comprehensive control over the parameter space, further compounded by the necessity for dynamic tunability. Here, we demonstrate the occurrence of optical EPs when operating with an electrically tunable non-Hermitian metasurface platform that synergizes chiral metasurfaces with piezoelectric MEMS mirrors. Moreover, we show that, with a carefully constructed metasurface, a voltage-controlled spectral space can be finely tuned to access not only the chiral EP but also the diabolic point characterized by degenerate eigenvalues and orthogonal eigenstates, thereby allowing for dynamic topological phase transition. Our work paves the way for developing cutting-edge optical devices rooted in EP physics and opening uncharted vistas in dynamic topological photonics.
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Affiliation(s)
- Fei Ding
- Centre for Nano Optics, University of Southern Denmark, Campusvej 55, Odense DK-5230, Denmark
| | - Yadong Deng
- Centre for Nano Optics, University of Southern Denmark, Campusvej 55, Odense DK-5230, Denmark
| | - Chao Meng
- Centre for Nano Optics, University of Southern Denmark, Campusvej 55, Odense DK-5230, Denmark
| | - Paul C V Thrane
- Centre for Nano Optics, University of Southern Denmark, Campusvej 55, Odense DK-5230, Denmark
- SINTEF Microsystems and Nanotechnology, Gaustadalleen 23C, 0737 Oslo, Norway
| | - Sergey I Bozhevolnyi
- Centre for Nano Optics, University of Southern Denmark, Campusvej 55, Odense DK-5230, Denmark
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Yang Y, Badloe T, Song D, Park S, Rho J. Building an optics and photonics research ecosystem in South Korea: Collaborative innovation between academia and industry. LIGHT, SCIENCE & APPLICATIONS 2023; 12:289. [PMID: 38044357 PMCID: PMC10694129 DOI: 10.1038/s41377-023-01332-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Accepted: 11/07/2023] [Indexed: 12/05/2023]
Affiliation(s)
- Younghwan Yang
- Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea
| | - Trevon Badloe
- Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea
- Graduate School of Artificial Intelligence, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea
| | - Duheon Song
- Samsung Advanced Institute of Technology (SAIT), Suwon, 16678, Republic of Korea
- School of System Semiconductor Engineering, Yonsei University, Seoul, 03722, Republic of Korea
| | - Seongjin Park
- Pohang Iron and Steel Company (POSCO), Pohang, 37859, Republic of Korea
| | - Junsuk Rho
- Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea.
- Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea.
- POSCO-POSTECH-RIST Convergence Research Center for Flat Optics and Metaphotonics, Pohang, 37673, Republic of Korea.
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He W, Hu Y, Ren Z, Hu S, Yu Z, Wan S, Cheng X, Jiang T. Transient Loss-Induced Non-Hermitian Degeneracies for Ultrafast Terahertz Metadevices. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023; 10:e2304972. [PMID: 37897321 PMCID: PMC10754078 DOI: 10.1002/advs.202304972] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Revised: 09/16/2023] [Indexed: 10/30/2023]
Abstract
Non-Hermitian degeneracies, also known as exceptional points (EPs), have attracted considerable attention due to their unique physical properties. In particular, metasurfaces related to EPs can open the way to unprecedented devices with functionalities such as unidirectional transmission and ultra-sensitive sensing. Herein, an active non-Hermitian metasurface with a loss-induced parity-time symmetry phase transition for ultrafast terahertz metadevices is demonstrated. Specifically, the eigenvalues of the non-Hermitian transmission matrix undergo a phase transition under optical excitation and are degenerate at EPs in parameter space, which is accompanied by the collapse of chiral transmission. Ultrafast EP modulation on a picosecond time scale can be realized through variations in the transient loss at a non-Hermitian metasurface pumped by pulsed excitation. Furthermore, by exploiting the physical characteristics of chiral transmission EPs, a switchable quarter-wave plate based on the photoactive metasurface is designed and experimentally verified and realized the corresponding function of polarization manipulation. This work opens promising possibilities for designing functional terahertz metadevices and fuses EP physics with active metasurfaces.
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Affiliation(s)
- Weibao He
- College of Advanced Interdisciplinary StudiesNational University of Defense TechnologyChangsha410073P. R. China
| | - Yuze Hu
- Institute for Quantum Science and TechnologyCollege of ScienceNational University of Defense TechnologyChangsha410073P. R. China
| | - Ziheng Ren
- College of Advanced Interdisciplinary StudiesNational University of Defense TechnologyChangsha410073P. R. China
| | - Siyang Hu
- College of Advanced Interdisciplinary StudiesNational University of Defense TechnologyChangsha410073P. R. China
| | - Zhongyi Yu
- College of Advanced Interdisciplinary StudiesNational University of Defense TechnologyChangsha410073P. R. China
| | - Shun Wan
- College of Advanced Interdisciplinary StudiesNational University of Defense TechnologyChangsha410073P. R. China
| | - Xiang'ai Cheng
- College of Advanced Interdisciplinary StudiesNational University of Defense TechnologyChangsha410073P. R. China
| | - Tian Jiang
- Institute for Quantum Science and TechnologyCollege of ScienceNational University of Defense TechnologyChangsha410073P. R. China
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Qin J, Wang M, Qiu CW. Graphene metasurface hits the point. LIGHT, SCIENCE & APPLICATIONS 2023; 12:110. [PMID: 37156789 PMCID: PMC10167302 DOI: 10.1038/s41377-023-01159-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Exceptional points pose exceptional difficulties to access and encircle. By simply gating graphene, it is now easier to hit the exceptional point.
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Affiliation(s)
- Jiazheng Qin
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117583, Singapore
| | - Mengjia Wang
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117583, Singapore
| | - Cheng-Wei Qiu
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117583, Singapore.
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